Gas exchange and gas transport Flashcards
Describe partial pressure
- The pressure cintributed by a single gas in a mixture of gases
- Adding all the partial pressures together gives you the total pressure fo the gas mixture
Describe the passage of oxygen from the alveoli to when it binds with haemoglobin
Decribe the passage of oxygen from a capillary into a tissue
What factors control the rate of diffusion (fick’s law)
- The area of the barrier
- The diffusing ability of the gas
- The thickness of the barrier
- The partial pressure difference
Describe the difference in oxygen exchange when someone has fibrosis or oedema
- Thickness of the barrier has increased
Diffusion of oxygen is reduced
How is oxygen carried in the blood?
- Combined with haemoglobin
- small amount dissolved in plasma
What is % saturation?
The amount of oxygen bound to haemoglobin
This is different to oxygen content as someone might have a very low level of haemoglobin in their blood but 100% saturation
Why is the oxyhaemoglobin dissociation curve S shaped?
- The 4 sub units in haemoglobin react with oxygen in sequence
- Dissociation occurs in sequence also
When does the curve shift to the right?
- High temperature
- High levels of CO2
- Low pH
- presence of 2,3-BPG (chemical released on exercise)
When does the curve shift to the left?
- Low temperature
- Low partial pressure of CO2
- High pH
What are the effects of the curve shifting to the right?
Haemoglobin releases oxygen more readily into the tissues
In other words: there is more oxygen unloading
What is the effect of the curve shifting to the left?
Less oxygen unloading
What other factors affect the amount of oxygen unloading in the tissues? (apart from ones that shift the curve)
- Anaemia - less haemogobin available
- Presence of carbon monoxide - binds next to oxygen and doesn’t allow Hb to release oxygen
- Nitric oxide - binds noext to oxygen and is released with oxygen and is a very good vasodilater - often used when patients are anethnatised
